The coupling of ion mobility separation (“IMS”) and mass spectrometry (“MS”) in commercial instruments has provided useful tools across a wide range of analytical areas.
A known combined ion mobility separation Time of Flight mass spectrometer and method of operating such is disclosed in U.S. Pat. No. 6,992,283 (Micromass) wherein two dimensional (i.e. drift time and mass to charge ratio) nested data sets are generated. Since the timescale for time of flight separation is relatively short, multiple mass to charge ratio analyses can be performed during the course of a single ion mobility separation run.
Other known IMS-MS instruments are disclosed in WO 2005/043115 (Ionwerks), GB-2512738 (Micromass) and US 2014/048704 (Micromass). In US 2014/048704 (Micromass) ions exiting an ion mobility separation device are interfaced with a Time of Flight mass analyser using a travelling wave ion guide.
US 2007/0114382 (Clemmer) discloses an ion mobility separation-mass spectrometry instrument containing two adjacent drift regions.
A general consideration when coupling ion mobility separation and mass spectrometry is that the instrument must operate over markedly different pressure regimes. Typically, ion mobility separation devices are operated at pressures ranging from atmospheric pressure down to 0.1 mbar whereas mass analysers are typically operated at pressures less than 10−4 mbar. An intermediate ion transfer region is commonly provided which may include an ion guide. The intermediate ion transfer region may include a number of differentially pumped low or intermediate pressure regions operated at pressures between that at which the ion mobility separator and the mass analyser are operated. The intermediate pressure ion transfer region may also contain ion focussing optics which are used to condition the ion beam for mass analysis.
Other multi-stage mass spectrometer geometries are known. For instance, it is known to combine quadrupole analysers or filters with other separation devices.
US 2013/0214146 (Shimadzu) discloses a triple quadrupole instrument where a time delay introduced by a collision cell is used to obtain a relationship between the voltages applied to the first stage quadrupole and the mass to charge ratio of ions selected. This relationship can be used to calibrate neutral loss measurements.
GB-2512738 (Micromass) discloses adjusting a transit time through an interface ion guide to allow the mass filtering characteristics of a quadrupole to be switched.
GB-2421844 (Micromass) discloses a mass spectrometer comprising a travelling wave ion guide arranged downstream of a mass selective ion trap.
US 2012/0193526 (Kovtoun) discloses an ion interface for interfacing an ion trap to a Time of Flight mass analyser comprising multiple confinement cells.
GB-2485667 (Micromass) discloses a method of controlling hydrogen-deuterium exchange on a spectrum by spectrum basis by controlling ion residence times within a travelling wave device.
It is desired to provide an improved mass spectrometer and method of mass spectrometry.